Sulfonium salt compounds and initiators of polymerization

ABSTRACT

The present invention is related to sulfonium salt compounds useful as an initiator of cationic polymerization and represented by a following general formula (I): ##STR1## wherein R 1  is benzyl, phenyl, etc., R 2 , R 3  and R 4  are each independently hydrogen, alkyl, etc., R 5  is hydrogen, alkyl, phenyl, etc., R 6  is a group represented by a formula, --(CH 2 ) m  --R 11  wherein R 11  is COR 12 , COOR 13 , OR, 14 , nitrile, OCOR 15  or SOR 16 , wherein R 12 , R 13 , R 14 , R 15  and R 16  are each independently hydrogen, alkyl or phenyl, m is 0 or 1, and X represents SbF 6 , AsF 6 , PF 6  or BF 4 .

This application is a 371 of PCT/TP94/00953 filed Jun. 14, 1994.

FIELD OF THE INVENTION

The present invention is related to novel sulfonium salt compounds and initiators of cationic polymerization comprising said sulfonium salt compound. The cationic polymerizable composition comprising said initiator of polymerization can cure under heating in a short time, and the cured-product thereof shows to have excellent physical properties. Therefore, the cationic polymerizable composition can be suitably used for molding resins, casting resins, coating materials, adhesives, inks and so on.

BACKGROUND ART

As curing agents for epoxy resins, amine-containing compounds, carboxylic anhydride and mercapto compounds, all of which are being widely used for two-part system, have been known. In two-part system, however, it is necessary to mix each components in absolutely uniform, and time for several hours are required for resulting the curing.

In addition, there is another problem in the curing in two-part system such as difficulty in the production because of its short pot life as long as from several hours to several days due to consecutive continuance of curing reaction proceeding even at room temperature.

Whereas, boron fluoride and monoethyl amine combination have been known as an agent for curing epoxy resins in one-part system. However, there are problems in the curing such that temperature required for the curing is very high as much as 160° C. and time duration of from 1 to 8 hours is required for the completion of the curing.

Aiming at solving such problems described above, pyridinium salt compounds are disclosed in JP Laid-Opened No. Hei 1-299270. By using pyridinium salt compounds. The execution of curing in one-part system and shortening of time required for the curing could have been realized, however, another problem of high temperature required for the curing has not been improved.

Further to said pyridinium salt compounds, the following sulfonium salt compounds similar to the compounds specified in the present invention have been disclosed. ##STR2##

However, sulfonium salt compounds disclosed in both JP Laid-Opened No. 2-178319 and JP Patent Examined Gazette No. Sho 63-12092 are still requiring high temperature to complete curing, and therefore, it is difficult to obtain cured-products having good physical property when using epoxy resins being widely used, such as bisphenol A diglycidyl ether.

Besides, sulfonium salt compounds described in JP Patent Examined Gazette No. Sho 63-12092 are mostly prepared from sulfide compounds having low boiling point, and therefore, the sulfonium salt compound itself and the cured-product thereof give bad smell in most cases.

On the other hand, sulfonium salt compounds described in JP Laid-Opened No. Hei 2-196812 are prepared from aromatic sulfide compounds in solid, and therefore, those sulfonium salt compounds do not give bad smell. However, because of their physical state in solid, said sulfonium salt compounds have a problem in the solubility in monomer. In addition, physical properties of the cured-products therewith tend to be no good. Furthermore, it is not easy to use sulfonium salt compounds capable of curing resins at less than 150° C. in one-part system.

DISCLOSURE OF THE INVENTION

The inventors of the present invention had examined to find novel initiators of polymerization which do not have problems such as giving smell, can cure cationic polymerizable compounds in a short time at a low temperature, and can further furnish excellent physical properties to the cured-product therewith, thereby having completed the present invention.

Therefore, the present invention is directed to sulfonium salt compounds represented by a general formula (I); ##STR3## wherein R₁ is unsubstituted or substituted benzyl, unsubstituted or substituted naphthylmethyl, unsubstituted or substituted cinnamyl, 9-fluorenyl, or unsubstituted or substituted phenyl,

R₂ and R₃ are each independently hydrogen or alkyl;

R₄ is hydrogen, alkyl or phenyl,

R₅ is hydrogen, alkyl, alkenyl, phenyl or --(CH₂)_(n) --R₇ wherein R₇ is COOR₈, OR₉, nitrile or OCOR₁₀, wherein R₈, R₉ and R₁₀ are each independently hydrogen, unsubstituted or substituted alkyl, or phenyl, and n denotes 0 or 1,

R₆ is --(CH₂)_(m) --R₁₁ wherein R₁₁ is COR₁₂, COOR₁₃, OR₁₄, nitrile, OCOR₁₅ or SOR₁₆, wherein R₁₃, R₁₄, R₁₅ and R₁₆ are each independently unsubstituted or substituted alkyl or phenyl, and m denotes 0 or 1,

and X is Sb₆, AsF₆, PF₆ or BF₄, and initiators of cationic polymerization.

As substituents for each aromatic ring of benzyl, naphthylmethyl, cinnamyl and phenyl as represented by R₁, alkyl, such as methyl, ethyl, propyl and butyl, halogen, such as fluorine, chlorine, bromine and iodine, nitro, vinyl, hydroxy, alkoxy, such as methoxy and ethoxy, alkanoyl, such as methoxycarbonyl and phenoxycarbonyl, and acyl, such as acetoxy and benzoyl, can be exemplified.

Further, as substituents for α-position of benzyl, alkyl, such as methyl, ethyl, propyl and butyl, halogen, such as fluorine, chlorine, bromine and iodine, alkanoyl, such as methoxycarbonyl and phenoxycarbonyl, and phenyl, can be exemplified.

As substituents for alkyl as represented by R₈, R₉, R₁₀, R₁₂, R₁₃, R₁₄, R₁₅ and R₁₆, halogen, such as fluorine, chlorine, bromine and iodine, nitro, alkoxy, such as methoxy and ethoxy, vinyl, phenyl and the like can be exemplified. In addition, among the substituents recited above, alkyl, alkoxy, phenyl, etc. may be substituted by the same substituents as described above. Again, as substituents for phenyl, alkyl, such as methyl, ethyl, propyl and butyl, halogen, such as fluorine, chlorine, bromine and iodine, nitro, alkoxy, such as methoxy and ethoxy, and cyano can be exemplified.

For X, SbF₆ is the most preferable group among SbF₆, AsF₆, PF₆ and BF₄.

The sulfonium salt compounds of the present invention can be obtained according to reaction equations as shown hereinbelow. ##STR4## wherein A is halogen or ##STR5## wherein R₅ ' is hydrogen or lower alkyl, B is R₅ '--CH₂ OSO₃ or ##STR6##

Both reactions of (1) and (2) are carried out for the time duration of from several hours to a dozen of days at a temperature of from room temperature to 80° C., and in an organic solvent, such as methanol, acetonitrile and dioxane, if required. Also, it is preferable to carry out the reactions by using each compounds being in approximately equimolar concentration, respectively.

The objective compounds can be obtained by passing sequential procedure comprising of dissolving the compounds having formulas (I') and (II") obtained by the reactions as described above into water or water-organic solvent system, such as water-methanol, adding a compound represented by a general formula MX(V), wherein M denotes an alkaline metal, to the solution to allow to stand in a reaction while stirring vigorously, and separating precipitated-substance in liquid or solid state.

For the representative examples of the sulfonium salt compounds of the present invention, the followings are exemplified. In each formulas, X represents any of SbF₆, AsF₆, PF₆ or BF₄. ##STR7##

In the present invention, a compounding ratio of the sulfonium salt compound respective to 100 parts of the cationic polymerizable compound is in a range of from 0.01 to 20 parts, and preferably from 0.1 to 10 parts. If said compounding ratio is less than the above range, curing capability of the cationic polymerizable compound deteriorates, while the advantageous physical property of the cured-product deteriorates if said compounding rate exceeds the above range.

The cationic polymerizable compound comprising the sulfonium salt compound of the present invention can be easily cured under heating.

For carrying out thermo-setting, a temperature in a range of from 30° to 200° C., preferably from 50° to 180° C., can be applied.

The cationic polymerizable compound comprising the sulfonium salt compound of the present invention can be easily cured in a short time under irradiation with ionizing radiation, such as α-ray, β-ray, γ-ray, neutron beam, X-ray and accelerating electronic ray. For curing the cationic polymerizable compound with ionizing radiation, a radiation dose of from 0.5 to 60M rad, and preferably from 1 to 50M rad, is normally applied to the compound.

In addition, it is also possible to result photo-setting of the cationic polymerizable compounds comprising the sulfonium salt compound of the present invention by additionally using a phenol sensitizer, such as 4-methoxy phenol, 4-methoxy-l-naphthol and 2-hydroxy benzofuran, or an aromatic secondary or tertiary amine sensitizer, such as phenothiazine, N,N'-diphenyl-p-phenylenediamine and N,N'-dimethylamino ethyl benzoate, in combination with the sulfonium salt compound.

The sulfonium salt compound of the present invention is normally used alone, but it may also be used in combination with other initiator of cationic polymerization. Also, the sulfonium salt compounds of the present invention may be used with any adding of reactive diluent, cure accelerator, solvent, pigment, dye, coupling agent, inorganic filler, carbon fiber, glass fiber and surface active agent.

The initiator of polymerization of the present invention is a type suitable for chain polymerization, and therefore, it can result polymerization and curing of cationic polymerizable compounds in a short time. Furthermore, the initiator itself gives less smell or almost no-smell since it contains groups, such as hydroxy, carboxy, ester and sulfinyl, in the molecule, and decomposed-product of the initiator gives less smell or no-smell as well. Moreover, the initiator of polymerization containing those groups as described above tends to have good solubility in monomer, and cationic polymerizable compound comprising said initiator acquires improved storage stability. In addition thereto, by changing the substituents in the chemical formula of the initiator, it becomes possible to set an optional curing temperature, thereby allowing the cured-product to have excellent physical property owing to the decrease of inhibitory effect on cationic polymerization caused by the decomposed-product of the initiator being remained.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention is further described with referring to Examples and Comparative Examples. However, it should be noted that the present invention shall not be limited to the scope specified in the Examples described hereinbelow.

EXAMPLE 1 Synthesis of methyl-sulfonylmethylbenzylmethyl sulfonium hexafluoroantimonate (Compound No. 1) ##STR8##

6.21 g of methylmethylsulfinylmethyl sulfide and 17.10 g of benzyl bromide were mixed, and were then allowed to stand in reaction at 50° C. for five months. The compound obtained was washed with ether, dried at 40° C. under reduced pressure, affording a precursor, methylsulfinylmethylbenzylmethyl sulfonium bromide. Yield: 26%.

1.48 g of methylsulfinylmethylbenzylmethyl sulfonium bromide was dissolved into a mixed solution of 5 g of distillated water and 2 g of ethyl ketone (herein after referred to as MEK). Then, 1.55 g of sodium hexafluoroantimonate was added to the solution, then stirred throughly. To this solution, 45 g of distillated water was added, then the solution was stirred throughly and subsequently cooled. The compound precipitated was separated by filtration, then dried at 40° C. under reduced pressure. Yield: 56%

Spectral data of the compound obtained was as follows.

IR(KBr, cm⁻¹): 3038, 1498, 1458, 1428, 1050, 775, 706, 660

EXAMPLE 2 2-hydroxyethylbenzylmethyl sulfonium hexafluoroantimonate (Compound No. 3) ##STR9##

8.41 g of 4-hydroxyethylbenzyl sulfide and 6.31 g of dimethyl sulfuric acid were mixed, then allowed to stand in reaction at 50° C. for seven days. The compound obtained was washed with ether, dried at 40° C. under reduced pressure, affording a precursor, 2-hydroxyethylbenzylmethyl sulfonium sulfate. Yield: 99%.

2.94 g of 2-hydroxyethylbenzylmethyl sulfonium sulfate was dissolved into a 15 g of distillated water. To this solution, 3.30 g of sodium hexafluoroantimo nate was added, then the solution was stirred throughly and subsequently cooled.

The compound precipitated in the solution was separated and was then dried at 40° C. under reduced pressure. Yield: 71%

Spectral data of the compound obtained was as follows.

IR(KBr, cm⁻¹): 3580, 1498, 1458, 1424, 1068, 773, 704, 660

The representative examples of the compounds of the present invention prepared according to the same procedure as described above are shown in Table 1, including the compounds prepared in the Examples 1 and 2.

                                      TABLE 1                                      __________________________________________________________________________                    ##STR10##                                                                                                               ##STR11##              Compound No.                                                                           R.sub.1        R.sub.2                                                                           R.sub.3                                                                          R.sub.4                                                                           R.sub.5 R.sub.6     X   IR (KBr                 __________________________________________________________________________                                                            cm.sup.-1)               1                                                                                      ##STR12##     H  H H  H       SOCH.sub.3  SbF.sub.6                                                                          3038, 1498, 1458                                                               1428, 1050, 775                                                                706, 660                 2                                                                                      ##STR13##     H  H H  H       CH.sub.2 CO.sub.2 H                                                                        SbF.sub.6                                                                          1723, 1498, 1458                                                               1423, 1251, 1189                                                               773, 704, 660            3                                                                                      ##STR14##     H  H H  H       CH.sub.2 OH SbF.sub.6                                                                          3580, 1498, 1458                                                               1424, 1068, 773                                                                704, 660                 4                                                                                      ##STR15##     H  H H                                                                                  ##STR16##                                                                             CH.sub.2 OH SbF.sub.6                                                                          3495, 1600, 1585                                                               1500, 1457, 1436                                                               1288, 1213, 1179                                                               1087, 888, 770                                                                 703, 662                 5                                                                                      ##STR17##     H  H H  HOCH.sub.2                                                                             CH.sub.2 OH SbF.sub.6                                                                          3570, 1497, 1456                                                               1420, 1365 1116                                                                752, 703, 660            6                                                                                      ##STR18##     H  H H  H       CH.sub.2 CO.sub.2 H                                                                        SbF.sub.6                                                                          1718, 1594, 1490                                                               1435, 1271, 1221                                                               1070, 1013, 841                                                                725, 660                 7                                                                                      ##STR19##     H  H H  H       CH.sub.2 OH SbF.sub.6                                                                          3577, 2944, 1505                                                               1457, 1424, 1119                                                               1069, 830, 660           8                                                                                      ##STR20##     H  H H  H       CH.sub.2 OH SbF.sub.6                                                                          3581, 1474, 1425                                                               1400, 1209, 1138                                                               1035, 831, 660           9                                                                                      ##STR21##     H  H H  CH.sub.3                                                                               CH.sub.2 OH SbF.sub.6                                                                          3573, 2979, 2944                                                               1505, 1456, 1423                                                               1119, 829, 661          10                                                                                      ##STR22##     H  H H  H       CH.sub.2 CO.sub.2 CH.sub.3                                                                 SbF.sub.6                                                                          3032, 1735, 1496                                                               1440, 1373, 1244                                                               1210, 710, 660          11                                                                                      ##STR23##     H  H H  H       CH.sub.2 OCOCH.sub.3                                                                       SbF.sub.6                                                                          3029, 1747, 1598                                                               1495, 1426, 1388                                                               1230, 1097, 843                                                                660                     12                                                                                      ##STR24##     H  H H                                                                                  ##STR25##                                                                             CH.sub.2 OH SbF.sub.6                                                                          3572, 2966, 1659                                                               1609, 1496, 1457                                                               1415, 1285, 1108                                                               1067, 907, 770                                                                 775, 709, 658           13                                                                                      ##STR26##     H  H H  H                                                                                       ##STR27##  SbF.sub.6                                                                          2933, 1738, 1498                                                               1459, 1425, 1384                                                               1318, 1244, 1203                                                               1002, 768, 703                                                                 662                     14                                                                                      ##STR28##     H  H H  H       CH.sub.2 OH SbF.sub.6                                                                          3544, 3035, 1481                                                               1425, 1120, 1049                                                               753, 661                15                                                                                      ##STR29##     H  H H  H       CH.sub.2 CO.sub.2 H                                                                        SbF.sub.6                                                                          3035, 1723, 1495                                                               1424, 1349, 1244                                                               1198, 1165, 1046                                                               754, 660                16                                                                                      ##STR30##     H  H H  H       CH.sub.2 CO.sub.2 CH.sub.3                                                                 SbF.sub.6                                                                          3033, 1738, 1493                                                               1440, 1374, 1245                                                               1211, 1047, 752                                                                702, 660                17                                                                                      ##STR31##     H  H H  H       CH.sub.2 CO.sub.2 CH.sub.3                                                                 SbF.sub.6                                                                          3035, 1738, 1440                                                               1374, 1246, 1211                                                               1046, 740, 659          18                                                                                      ##STR32##     H  H H  H       CH.sub.2 OH SbF.sub.6                                                                          3559, 3033, 1600                                                               1425, 1119, 1049                                                               754, 701, 659           19                                                                                      ##STR33##     H  H H  H       CH.sub.2 CO.sub.2 H                                                                        SbF.sub.6                                                                          3030, 1718, 1647                                                               1600, 1494, 1418                                                               1245, 1193, 977                                                                757, 701, 661           20                                                                                      ##STR34##     H  H H  H       CH.sub.2 OH SbF.sub.6                                                                          3573, 1599, 1494                                                               1423, 1118, 1063                                                               976, 757, 705 660       21                                                                                      ##STR35##     H  H H  H       CH.sub.2 OH SbF.sub.6                                                                          3575, 1598, 1513                                                               1423, 1117, 1071                                                               806, 781, 661           22                                                                                      ##STR36##     H  H H  H       CH.sub.2 CO.sub.2 C.sub.2 H.sub.5                                                          SbF.sub.6                                                                          1727, 1480, 1450                                                               1425, 1379, 1267                                                               1197, 983, 760                                                                 657                     23                                                                                      ##STR37##     H  H H  H       CH.sub.2 CO.sub.2 C.sub.2 H.sub.5                                                          SbF.sub.6                                                                          2945, 1736, 1577                                                               1482, 1399, 1318                                                               1279, 1202, 1098                                                               1013, 828, 749                                                                 661                     24                                                                                      ##STR38##     H  H H  H                                                                                       ##STR39##  SbF.sub.6                                                                          2960, 1732, 1598                                                               1494, 1464, 1413                                                               1372, 1241, 1207                                                               1097, 1017, 843                                                                732, 661                25                                                                                      ##STR40##     H  H H  H       CH.sub.2 OCOC.sub.2 H.sub.4                                                    CO.sub.2 H  SbF.sub.6                                                                          2953, 1734, 1598                                                               1497, 1413, 1360                                                               1208, 1159, 1097                                                               1018, 845, 733                                                                 661                     26                                                                                      ##STR41##     H  H H  H                                                                                       ##STR42##  SbF.sub.6                                                                          2951, 1724, 1599                                                               1494, 1413, 1286                                                               1261, 1201, 1125                                                               1077, 1017, 746                                                                661                     27                                                                                      ##STR43##     H  H H  H                                                                                       ##STR44##  SbF.sub.6                                                                          2973, 1733, 1498                                                               1458, 1424, 1373                                                               1243, 1205, 1081                                                               773, 705, 660           28                                                                                      ##STR45##     H  H H  H                                                                                       ##STR46##  SbF.sub.6                                                                          2960, 1732, 1459                                                               1399, 1372, 1309                                                               1240, 1201, 1016                                                               728, 661                29                                                                                      ##STR47##     H  H H  H       CO.sub.2 C.sub.2 H.sub.5                                                                   SbF.sub.6                                                                          3488, 1736, 1602                                                               1587, 1503, 1438                                                               1317, 1290, 1202                                                               1181, 1019, 838                                                                661                     30                                                                                      ##STR48##     H  H H  H                                                                                       ##STR49##  SbF.sub.6                                                                          3516, 1729, 1602                                                               1588, 1502, 1441                                                               1286, 1219, 1181                                                               1091, 997, 841                                                                 663                     31                                                                                      ##STR50##     H  H H  H       OCH.sub.3   SbF.sub.6                                                                          3035, 2941, 1593                                                               1494, 1427, 1045                                                               999, 751, 658           32                                                                                      ##STR51##     H  H H  H       CH.sub.2 CO.sub.2 C.sub.2 H.sub.5                                                          SbF.sub.6                                                                          1733, 1601, 1585                                                               1503, 1450, 1372                                                               1294, 1198, 1084                                                               1014, 841, 661          33                                                                                      ##STR52##     H  H H  HO.sub.2 CCH.sub.2                                                                     CH.sub.2 CO.sub.2 H                                                                        SbF.sub.6                                                                          3032, 1733, 1498                                                               1423, 1374, 1247                                                               1207, 1004, 774                                                                705, 660                34                                                                                      ##STR53##     H  H H  H                                                                                       ##STR54##  SbF.sub.6                                                                          2974, 1733, 1598                                                               1495, 1413, 1373                                                               1243, 1207, 1097                                                               843, 661                35                                                                                      ##STR55##     H  H H  H                                                                                       ##STR56##  SbF.sub.6                                                                          2960, 1730, 1459,                                                              1424, 1245, 1201                                                               704, 662                36                                                                                      ##STR57##     H  H H  H                                                                                       ##STR58##  SbF.sub.6                                                                          2941, 1740, 1459                                                               1382, 1318, 1200                                                               1082, 704, 660          37                                                                                      ##STR59##     H  H H  H                                                                                       ##STR60##  SbF.sub.6                                                                          2941, 1738, 1598                                                               1495, 1384, 1318                                                               1199, 1098, 661         38                                                                                      ##STR61##     H  H H  H                                                                                       ##STR62##  SbF.sub.6                                                                          2935, 1737, 1598                                                               1495, 1317, 1198                                                               1098, 662               39                                                                                      ##STR63##     H  H CH.sub.3                                                                          H       CO.sub.2 C.sub.2 H.sub.5                                                                   SbF.sub.6                                                                          2946, 1733, 1450                                                               1314, 1198, 1079                                                               754, 687,               __________________________________________________________________________                                                            659                

<Test on Curing Capability>

A compound according to the present invention was respectively added to ERL-4221 (alicyclic epoxy compound manufactured by UCC) and UVR-6410 (glycidyl-type epoxy compound manufactured by UCC) at a compounding ratio of 2.5 parts by weight respective to 100 parts by weight of either ERL-4221 or UVR-6410 to prepare a compounded composition. With the compounded compositions, DSC measurement were carried out to determine the top temperatures of exothermic peak, respectively. The followings are the condition for the DSC measurement, and the results obtained were shown in Table 2.

Apparatus for measuring DSC: DSC 220C (Manufactured by Seiko Densi Kogyo)

Atmosphere: In Flow of Nitrogen Gas at a speed of 30 ml/min.

Speed of Temperature Elevation: 10° C./min.

Sample Amount: 0.3-0.8 mg

Comparative Sample 1

For the comparative sample to the compound of the present invention, benzyl-4-cyanopyridinium hexafluoroantimonate was used as an initiator of polymerization, then DSC measurement was carried out for a composition compounded with said initiator according to the same procedure as described above in Test on Curing Capability.

Comparative Sample 2

For the comparative sample to the compound of the present invention, N-benzyl-N-methyl anilinium hexafluoroantimonate was used as an initiator of polymerization, then DSC measurement was carried out for a composition compounded with said initiator according to the same procedure as described above in Test on Curing Capability.

Comparative Sample 3

By using benzyl tetramethylene sulfonium hexafluoroantimonate as an initiator of polymerization, a compounded-composition was prepared by mixing it with either ERL-4221 or UVR-6410 according to the same procedure as described in Test on Curing Capability. DSC measurement was carried out for said composition to determine the top temperatures of exothermic peak (See Comparative Examples 1 through 3, and Comparative Examples 4 through 6). All results obtained are shown in Table 2.

                  TABLE 2                                                          ______________________________________                                                                 Top Temp. of DSC Peak                                  Compound No. Epoxy Resin                                                                               (°C.)                                           ______________________________________                                          1           ERL-4221   140                                                     2           UVR-6410   142                                                     3           ERL-4221   139                                                     4           UVR-6410   151                                                     5           ERL-4221   152                                                     6               "      132                                                     7           UVR-6410   160                                                     8           ERL-4221   155                                                     9           UVR-6410   153                                                    10           ERL-4221   152                                                    11               "      147                                                    12               "       96                                                    13           UVR-6410   125                                                    14           ERL-4221   100                                                    15               "      133                                                    16           UVR-6410   145                                                    17           ERL-4221   149                                                    18               "      105                                                    19           UVR-6410   104                                                    20           ERL-4221   102                                                    21           UVR-6410   150                                                    22           ERL-4221   140                                                    23               "      133                                                    24               "      122                                                    25               "      149                                                    26           ERL-4221   149                                                    27           UVR-6410   128                                                    28           ERL-4221   126                                                    29               "      153                                                    30               "      144                                                    31           ERL-4221    87                                                    32               "      152                                                    33               "      133                                                    34           UVR-6410   132                                                    35           ERL-4221   126                                                    36           UVR-6410   112                                                    37               "      115                                                    38               "      127                                                    39           ERL-4221   148                                                    Comparison Sample 1                                                                         ERL-4221   174                                                    "            UVR-6410   227                                                    Comparison Sample 2                                                                         ERL-4221   168                                                    "            UVR-6410   201                                                    Comparison Sample 3                                                                             "      189                                                    ______________________________________                                    

<Advantageous Physical Property of Cured Products>

Sulfonium salt compound in an amount of 2.0 parts by weight respective to 100 parts of UVR-6410 was added to UVR-6410 to prepare a compounded composition. 10 g of the compounded composition were each distributed into Teflon cups, then were placed for 30 min. in an oven maintained at different temperature, respectively. The dynamic mechanical analysis (DMA) of cured-resin was measured, and temperature of glass transition (Tg) was determined from the peak of loss modulus, respectively.

The conditions for measuring DMA were as follows. The results are shown in Table 3.

Apparatus for measuring DMA: DMA 983 (TA Instrument Japan Inc.)

Frequency: 1 Hz

Speed of Temperature Elevation: 5° C./min.

                  TABLE 3                                                          ______________________________________                                         Compound No.                                                                              Temp. for Curing                                                                            Temp. of Glass Transition                              ______________________________________                                          6         130° C., 30 min.                                                                     141                                                    13          90° C., 30 min.                                                                     145                                                    22         150° C., 30 min.                                                                     129                                                    23            "         130                                                    27         110° C., 30 min.                                                                     144                                                    32         150° C., 30 min.                                                                     135                                                    34         130° C., 30 min.                                                                     143                                                    36          70° C., 30 min.                                                                     144                                                    38          90° C. × 30 min.                                                              141                                                    39         150° C. × 30 min.                                                              134                                                    ______________________________________                                    

Industrial Utilization of the Invention

The novel sulfonium salt compound of the present invention, which has substituents, such as COOR₈ and OR₉, at the carbon atoms being connected with each other via a carbon atom, which is directly bounding to a sulphur atom or methylene, is found to be effective as an initiator of polymerization for cationic polymerizable compounds. As can be seen from the Examples, Test on Curing Capability and Physical Property of Cured-Products, said sulfonium salt compound can polymerize and cure cationic polymerizable compounds under heating in a very short time and even at low temperature. Furthermore, by changing the substituents of said sulfonium salt compound, optional selection of temperature for curing becomes allowable and the synthesis of the sulfonium salt compounds can be further made easier and less costly.

The initiators of polymerization according to the present invention are each composed of a sulfonium salt compound, however, the sulfonium salt compound contains functional groups, such as hydroxy, carboxyl and ester group, and therefore the initiator gives less or no smell as well as the decomposed-products thereof. 

What is claimed is:
 1. Sulfonium salt compounds represented by a general formula (I); ##STR64## wherein R₁ is unsubstituted or substituted benzyl, unsubstituted or substituted naphthylmethyl, unsubstituted or substituted cinnamyl, 9-fluorenyl, or unsubstituted or substituted phenyl,R₂ and R₃ are each independently hydrogen or alkyl; R₄ is hydrogen, alkyl or phenyl, R₅ is hydrogen, alkyl, alkenyl, phenyl or --(CH₂)_(n) --R₇ wherein R₇ is COOR₈, OR₉, nitrile or OCOR₁₀, wherein R₈, R₉ and R₁₀ are each independently hydrogen, unsubstituted or substituted alkyl or phenyl, and n denotes 0 or 1, R₆ is --(CH₂)_(m) --R₁₁ wherein R₁₁ is COR₁₂, COOR₁₃, OR₁₄, nitrile, OCOR₁₅ or SOR₁₆, wherein R₁₂, R₁₃, R₁₄, R₁₅ and R₁₆ are each independently unsubstituted or substituted alkyl or phenyl, and m denotes 0 or 1, and X is Sb₆, AsF₆, PF₆ or BF₄.
 2. Initiators of polymerization comprising at least one of the sulfonium salt compounds represented by the general formula (I) as claimed in claim
 1. 